Covid-19 vaccines, what the new data on adverse reactions tell us


Aifa records 154 reports out of 100 thousand vaccinated: in 9 cases out of 10 they are non-serious reactions. First numbers on heterologous vaccination: 12 reports every 100 thousand doses

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IS was released today on sixth report of pharmacovigilance of Covid-19 vaccines, made by the Italian Medicines Agency (Aifa). The document contains an analysis of the data on all adverse reactions until the June 26, detected after the administration of anti-Covid vaccines. There are around 154 reports per 100 thousand vaccinated and almost the 90% of these findings concerns events not serious, such as pain at the injection site, temperature and fatigue. Today, moreover, data on suspicious reactions after the heterologous vaccination, the recent formula that combines two doses of different vaccines (the first with the AstraZeneca and the second with a vaccine a mRna). For now, the data indicate that there have been with the mix 12 reports every 100 thousand doses.

Adverse reactions in numbers

Aifa specifies that the report always speaks of “suspected adverse reactions “, that is, of events observed after vaccination, whose link with the vaccine in many cases is possible but in others it may prove absent. In all, there have been approximately 76,000 reports of suspected adverse reactions out of over 49 million doses administered. In the87,9% it’s about episodes of mild intensity a moderate, while in 11.9% who made the report estimated theentity as severe. But we must not think that it is always a question of very serious events like those rare forms of thrombosis of which we have spoken. Conversely, as Aifa explains, most severe events are flu-like syndromes with very intense symptoms: for example high fever e severe muscle aches.

What are the common effects and when do they appear

For all vaccines the most common reported effects are temperature, fatigue, headache, muscle and joint pain, injection site pain, chills and nausea. Furthermore, regardless of the vaccine type, dose and disorder presented, the reaction occurred in the majority of cases (approximately 80%) on the same day vaccination or the next day and only more rarely beyond the following 48 hours. In the case of the mRna vaccines (Pfizer-BioNTech and Moderna) the episodes, both mild and intense, were more frequent after the second dose, while in the case of viral vector vaccines such as AstraZeneca after the first.

The reports divided by type of vaccine

The new report includes all reports of adverse reactions from December 27, 2020, the start date of the vaccination campaign in Italy, until June 26. Almost 7 out of 10 adverse event reports are associated with the Pfizer-BioNTech, but simply because it is the most used in Italy (69% of reactions and the product was administered to about 70% of the population). Immediately after it arrives Vaxzevria of AstraZeneca (24.7% of reports and 17.3% of administered doses), Spikevax of Modern, with 5.2% of reports and 9.6% of doses administered, and finally the vaccine of Janssen (1.1% of reports and 2.5% of administered doses).

Heterologous vaccination

Today also for the first time comes official information and on a large sample of the population on the side effects associated with heterologous vaccination. Who has less than 60 years old and had already received the first dose of AstraZeneca’s Vaxzevria vaccine before new block in June in fact, he can choose whether to receive the recall always with Vaxzevria or to change product and switch to an mRna vaccine. More than 233 thousand Italians they received this combination mixed with vaccines. Within this sample, 86% of people received Pfizer-BioNTech’s second vaccine and the remaining 14% Moderna’s Spikevax. In all, there were 27 reports, a figure that compared to the unit of 100 thousand people is equivalent to 12 almost his 100 thousand. If compared to the number of administrations for each of the two products (Pfizer-BioNTech and Moderna) of the second dose, the proportion of effects is similar between the two. Three of these events were assessed to be of serious intensity by the person who made the report, but, as Aifa writes, “predominantly related to injection site pain e improving already at the time of reporting”.


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